In an information recording and reproduction apparatus recording information onto an information recording medium such as an optical disc, an optimum recording power of a laser light used for recording operation is set by an OPC (Optimum Power Calibration) process in correspondence to a type of the optical disc, a type of the information recording and reproduction apparatus and a recording speed. Namely, calibration of the laser power is performed. Thereby, the appropriate recording operation can be realized. For example, when the optical disc is loaded and a writing command is inputted, light intensity is gradually switched in order, and data for test writing is recorded in an OPC area. Thereby, the so-called test writing process is executed. Afterward, the data for the test writing thus recorded is reproduced, and the reproduction result is judged by a predetermined evaluation standard. Thereby, the optimum recording power is set. An example of a determination method of the optimum recording power is disclosed in Patent Reference-1.
Meanwhile, a technique of increasing the recording speed (or reproduction speed) of the information is developed by increasing of a rotation speed of the optical disc. For example, as for a CD-R being an example of the optical disc, as the rotation speed of the optical disc is increased, the recording speed of the data is increased, e.g., 24-time high speed and 48-time high speed.
When the rotation speed of the optical disc is increased in this manner, it is preferable that the OPC process is executed at a liner speed corresponding to a recording track actually used for recording the data. However, since the OPC process is basically executed on the innermost circumferential side of the optical disc, the liner speed is the lowest at the same rotation speed. Therefore, the actual liner speed cannot be realized on the innermost circumferential side due to a specification or physical restriction of a motor for controlling the rotation. Particularly, at CLV (Constant Liner Velocity) at which the liner speed becomes constant in any recording area of the optical disc, the rotation speed on the innermost circumferential side becomes larger than that on the outermost circumferential side. Thus, on a DVD being an example of the optical disc, high-speed rotation of 12000 rpm is necessary on the innermost circumferential side, in order to realize the recording speed or the liner speed of 8-times higher, for example. Due to the specification of the motor, it is difficult to realize such high-speed rotation. It is technically problematic that such high-speed rotation causes damage of the optical disc. In addition, even if such high-speed rotation is realized, it is also technically problematic that a servo for controlling the motor becomes unstable and detection accuracy of asymmetry and a β value is lowered. So as to solve the above problems, such a technique that the OPC process is executed at the low rotation speed and the optimum recording power at the high-speed rotation is estimated and obtained based on the result is introduced to the CD-R being an example of the optical disc.
However, in the above method, since the optimum recording power at the time of the actual recording is determined (estimated) based on the test writing information in the recording power area different from that at the time of the actual recording, the determination accuracy of the optimum recording power is low. Therefore, when the optimum recording power is corrected at the time of the actual recording, the recording power is sometimes out of a power margin. Additionally, since accuracy of actual recording power information (a relation between the recording power and the asymmetry or the β value) obtained at the time of the test writing is low, the information cannot be used for calculation of recording power correction amount after starting of the actual recording, or even if the information is used, the calculation of the appropriate correction amount is difficult. Hence, it is impossible to effectively correct the recording power after starting of the actual recording.
Patent Reference-1: Japanese Patent No. 3159454